1. Field of the Invention
The present invention relates to an apparatus for multiplexing a line, and more specifically, to an apparatus for multiplexing a line and a data transmission method that improves data transmission efficiency.
2. Background of the Related Art
Related art intra-network systems are widely used in accordance with a rapid worldwide development of telecommunications technology. In a related art intra-network system, local area network (LAN) systems connect computers, telephones and facsimile machines. Data communication between various related art intra-networks can be performed wherein an apparatus for multiplexing a line is provided in each intra-network, and wherein each of the respective apparatuses for multiplexing a line are connected by a trunk.
FIG. 1 illustrates operations of the related art apparatus for multiplexing a line, including multiplexing during data transmission and demultiplexing during data reception. When multiplexing during data transmission, an input signal is generated. If the input signal is a voice signal generated from a telephone 10a, a signal from a facsimile machine 10b, or a signal from a modem 10d of a computer 10c, the signal is transmitted to a voice line connector 10 that modulates the signal by a pulse code modulation (PCM) mode and transmits the modulated signal to a multiplexer/demultiplexer 30. Thus, an input signal at 8 Kbps or 14.4 Kbps can be converted to the modulated signal at 64 Kbps.
However, if the input signal is a data signal generated by a computer 20a, the data signal is transmitted to a data line connector 20 that modulates the data signal by the PCM mode and transmits the modulated data signal to the multiplexer/demultiplexer 30.
The multiplexer/demultiplexer 30 respectively assigns channels to the modulated signal from the voice line connector 10 or the data line connector 20 by a time division multiplexing (TDM) mode, and outputs the modulated signal to an output line connector 40 that transmits the modulated and multiplexed signal to a trunk coupled to other apparatuses for multiplexing a line.
The TDM mode divides a number of data or digitized voice signals into a certain time (i.e., time slot) to multiplex a plurality of channels. Therefore, the related art apparatus for multiplexing a line assigns one time channel to each user application, and performs data transmission or reception through that channel. The assigned channel is maintained until the user application terminates data transmission or reception. Thus, during periods that a particular user application is inactive, the data handling capacity assigned to that user application will be wasted.
However, the related art apparatus has various problems and disadvantages. For example, the related art apparatus allows data transmission within a tolerance limit of an overall channel capacity, and when the number of users exceeds a threshold value of the overall channel capacity for a particular time, a standby time period is required for data communication between subscribers in different intra-networks. Additionally, quality of service may deteriorate due to a heavy load on the related art apparatus. To solve this problem, the overall channel capacity can only be increased by increasing the number of the related art apparatuses and the number of trunks, but additional costs and construction work time will result.